Brookhaven Spotlights: News From the April 2002 American Chemical
Society Meeting

NOTE
TO EDITORS: “Brookhaven Spotlights” is issued periodically to
bring you up to date on some of the latest newsworthy developments at
the U.S. Department of Energy’s Brookhaven National Laboratory. The
selected briefings below describe research that Brookhaven scientists
presented at the American Chemical Society meeting held April 7-11,
2002, at the Orange County Convention Center in Orlando, Florida.

Nanocatalysts and Atmospheric Chemistry

Brookhaven chemists have developed computer simulations describing the
atomic-level mechanisms of chemical reactions involved in the combustion
of hydrocarbon fuels, and the role of chemicals a billionth of a meter in
size in speeding up these reactions.

The reaction of hydroxyl radicals – a major cause of smog and
atmospheric pollution – with carbon monoxide to produce carbon dioxide is
poorly understood, despite being the primary mechanism for removal of
carbon monoxide from the atmosphere. When the hydroxyl radical (OH) and
carbon monoxide (CO) combine, they form a transient molecule, HOCO, that
later breaks into carbon dioxide and hydrogen.

Chemists Hua-Gen Yu and James T. Muckerman

Having previously simulated the reaction of OH with CO, chemist James
T. Muckerman and research associate Hua-Gen Yu have now simulated how
light breaks the bonds between the atoms of the HOCO molecule. They found
that when light excites a specific vibrational state of the OH bond, HOCO
breaks into both hydroxyl radical and carbon monoxide, and carbon dioxide
and hydrogen. The most interesting result, Yu said, is that when light
hits the OH bond, it is broken in only one-third of the cases, and the
nearby CO bond is split the rest of the time. “This result may seem
counter-intuitive,” he said, “but it is due to the fact that the bonds are
coupled, and what affects one bond affects its neighbors as well.”

Muckerman said that the new calculation methods for many-atom systems
will be important in studying how nanocatalysts – chemicals the size of a
billionth of a meter – speed up chemical reactions. “Nobody really
understands how nanocatalysts work,” Muckerman said. “So we are now using
our simulations to investigate the role of these catalysts at the atomic
level.”

Helping to Fuel Efficient Electric Vehicles

Brookhaven scientists have developed a new method of creating catalysts
that could allow the production of cheaper and more efficient fuel cells –
highly efficient electrical energy sources that may one day replace cars’
internal combustion engines.

Like a regular battery, a fuel cell produces electricity as a result of
chemical reactions. Unlike a battery, however, a fuel cell does not
require charging, but instead produces energy by feeding hydrogen and
oxygen onto metal-based plates called electrodes. The chemical energy is
converted into electrical energy as the electrons flow between the
electrodes.

To
maximize the chemical reactions inside the fuel cell, both electrodes
contain a catalyst, or “electrocatalyst.” One of the most efficient
electrocatalysts is made of an alloy of platinum and ruthenium, but its
efficiency is reduced by carbon monoxide deposits formed on the platinum
as a by-product of the hydrogen-oxygen reaction. The new method developed
by the Brookhaven team, led by chemist Radoslav Adzic, reduces the amount
of platinum present in the catalyst, thus limiting carbon monoxide
accumulation and improving fuel cell performance.

In the new method, platinum atoms are deposited on the surface of tiny
ruthenium crystalline particles. In contrast, typical platinum-ruthenium
alloy catalysts have platinum throughout. “Our method very likely makes
almost all of the platinum atoms available to react with the hydrogen,”
Adzic said.

New PET imaging studies at Brookhaven are helping scientists to
understand how a drug’s “handedness” affects its performance in the human
body, and may lead to the development of more effective pharmaceuticals.

Just like a person, drug molecules can be “lefties” or “righties,” a
property determined by the spatial orientation of their atoms. Mirror
images of each other, each version of a particular drug molecule contains
the identical atoms and identical chemical and physical properties, but
can have different effects in the human body. “Our body’s proteins can
distinguish the difference between left- and right-handed molecules and
react accordingly,” said chemist Yu-Shin Ding. “The results can be quite
dramatic.”

Most drugs are mixtures of the lefty and righty versions of the same
molecule. In the case of Ritalin, known also as methylphenidate, Ding and
her research team found that the right-handed version is responsible for
the therapeutic effects of the drug. As a result, if the right-handed
version were to be isolated and produced as a pharmaceutical drug,
patients may only have to take half of the current dose to get the same
effect. This kind of selective production can also help reduce unwanted
drug side effects – L-dopa, used to treat Parkinson’s disease, is one
example of a left-handed molecule being used because the right-handed
version has associated side effects.

Ding and her colleagues are currently studying a host of other drugs to
determine the “handedness” effect, including methadone; GVG, a drug that
has shown promise in the treatment of addiction; and BPA, a drug used for
the treatment of melanoma and brain tumors .

Mapping Human Enzyme Activity

New radiotracers developed by Brookhaven scientists are helping to map
an important enzyme’s role in the human body, studies that may facilitate
the development of new drugs and lead to a better understanding of brain
and body chemistry.

Chemist
Joanna Fowler and colleagues have developed radiotracers for mapping the
enzyme monoamine oxidase (MAO), a molecular target of drugs used to treat
depression and Parkinson’s disease. Using a medical imaging technique
called positron emission tomography (PET), Fowler had previously
discovered that smokers, who are less prone to Parkinson’s disease, have
an average of 40 percent less MAO than nonsmokers. MAO breaks down
dopamine, a brain chemical that is important in movement, motivation, and
reward.

MAO has an equally important role in the body, where it breaks down
potentially dangerous toxins in food. Until now, however, scientists have
not been able to image the enzyme’s activity in organs other than the
brain. Fowler and her team are now using these Brookhaven-developed
radiotracers to look at MAO activity in other organs and determine how MAO
levels are affected by smoking and interaction with various drugs. This
work may help lead to the development of new drugs to treat or prevent
Parkinson’s disease, and help identify other factors that influence MAO
levels, including aging and smoking, and their possible implications in
health and disease.

“This is important knowledge,” said Fowler, who will receive the ACS’s
Glenn T. Seaborg award on Monday for this and other brain chemistry work.
“We’re now able to look at the effect of various drugs on the enzyme
directly in the body.”

The
U.S. Department of Energy's Brookhaven National Laboratory conducts
research in the physical, biomedical, and environmental sciences, as
well as in energy technologies. Brookhaven also builds and operates
major facilities available to university, industrial, and government
scientists. The Laboratory is managed by Brookhaven Science
Associates, a limited liability company founded by Stony Brook
University and Battelle, a nonprofit applied science and technology
organization.